General Motors this morning introduced the extra high-performance Corvette Z06, a fit-for-the-street race car boasting at least 625 horsepower. The 2015 Corvette Z06, revealed in a press conference at the Detroit auto show, shares an aluminum frame with its high-profile sister, the Corvette Stingray, but it's distinguished by an 6.2-liter "supercharged" V-8 mated with a custom-made eight-speed automatic transmission. The Z06 was GM's fastest car ever when engineers tested it at the Milford Proving Grounds, Corvette chief engineer Tadge Juechter told reporters. "It's got more downforce than any vehicle General Motors has ever tested from any manufacturer," Juechter said.